This paper presents a methodology for a systematic, robust and conservative ecological risk assessment for estimating environmental consequences and associated risk from ambient air concentrations of atmospheric pollutants and air toxics (also referred to as criteria pollutants and hazardous atmospheric pollutants in the United States legislation respectively), as arising from industrial activities. The paper details the main steps of the risk assessment process and makes a contribution in deriving conservative and safe Reference Concentrations (RfC) such as No Observed Adverse Effect Level (NOAEL) and Lowest Observed Adverse Effect Level (LOAEL) for fauna in their natural habitat, using published scientific dose-response toxicological studies with laboratory animals. It then uses these derived RfCs to determine step changes in consequence levels, from incidental to major, in order to complete the risk assessment. A similar approach is used to assess impacts on the marine environment. This methodology is repeatable and robust and can be applied as a screening level environmental risk assessment to establish conformance to legally postulated levels of acceptable environmental consequences, where available, or acceptable levels of environmental risk, associated with air quality.

Project Background and Setting

The Gorgon Project, operated by Chevron Australia Pty Ltd on behalf of the Gorgon Joint Venture Participants, will develop the Gorgon and Jansz-Io gas-condensate fields, located offshore the north-west corner of Western Australia (WA) (see Figure 1). The approved development will include subsea gathering systems and pipelines delivering the gas to a 15 million tonne per annum (MTPA) liquefied natural gas (LNG) Gas Treatment Plant (GTP) located on the east coast of Barrow Island (BWI), which is a Class A nature reserve, lying some 60 km north of the Australian mainland. The Gorgon Project is an unique LNG Project in that it will also encompass the largest industrial scale acid gas injection undertaking in the world to date whereby some 4.2 MTPA of CO2 and other acid gas components (i.e. residual methane, (CH4), volatile organic compounds (VOCs) and hydrogen sulphide (H2S) removed from the natural gas, will be liquefied and injected via three injection centres in the Dupuy Formation below BWI in the Operations Phase of the Project.